scenario assessment of solid waste management for izmir ...in izmir, approximately 5100 tons of...

Scenario Assessment of Solid Waste Management for Izmir based on the Methodology of Material Flow

Analysis

By

MSc. Nur ONDER

Supervisor

Prof. Dr. Paul Hans Brunner

Research Centre of Waste and Resource Management

Institute of Water Quality, Resources and Waste Management

Vienna, July 2013

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TABLE OF CONTENT

Preface .................................................................................................................................... v

Abstract ................................................................................................................................... vii

1 Introduction ........................................................................................................................ 1

2 Aim of Study and Research Questions .............................................................................. 5

3 Methodology of Material and Substance Flow Analysis ................................................... 11

4 Process Description ......................................................................................................... 13

4.1 Theory and Technology of Composting .................................................................... 13

4.2 Theory and Technology of Anaerobic Digestion ....................................................... 28

4.3 The Definition of Microwave Pretreatment ................................................................ 44

5 Scenario Development and Definitions ............................................................................ 49

5.1 Status Quo of Solid Waste Management in Izmir .................................................... 50

5.1.1 Scenario 1: Composting ...................................................................................... 57

5.1.2 Scenario 2a: Anaerobic Digestion and Composting ............................................ 58

5.1.3 Scenario 2b: Anaerobic Digestion with Microwave Pretreatment and

Composting ......................................................................................................... 60

6 Cost Analysis for all scenarios ......................................................................................... 67

7 Conclusions ..................................................................................................................... 77

8 References ...................................................................................................................... 79

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Preface

This report has been elaborated by Nur Onder during her internship at the FAR/Vienna

University of Technology. The main goal of this practicum was to learn the methodology of

material flow analysis, the software STAN, economic analysis and scenario analysis. Since

the data base for Izmir was not fully developed yet, uncertainies of this report are significant.

Thus, the numerical results are less important than the methodological approach, which can

and should be applied for an in depth study based on solid data in Izmir and elsewhere.

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Abstract

In Izmir, approximately 5100 tons of municipal solid waste (MSW) are generated per

day. Between 1992 and 2013, more than 32 million tons of wastes have been disposed of in

the Harmandali landfill. This practice poses a public health hazard due to landfill gases, odors

and dust formation, and untreated leachates, which are discharged into the Gulf of Izmir, may

reach surface and groundwater, and pollute soils, too.

The aim of this study is to assess the current solid waste management system of

Izmir, and to compare various scenarios for integrated MSW management based on

biological waste treatment and the methodology of material flow analysis. Aerobic as well as

anaerobic treatment processes and combinations thereof are taken into account. The

following research questions are investigated: What are the flows of wastes, products and

emissions of key substances for the status quo and selected scenarios? What are the

transfer coefficients for the goods and substances of the various processes investigated?

What are the operational and investment costs of the scenarios? How do the scenarios

perform in their total costs when compared to the status quo? The results are as follows:

Biological treatment could decrease the volume of MSW landfill in Izmir by 40%. The

amount of organic constituents landfilled will be reduced by 95% and greenhouse gas

emissions from landfilling and biological treatment will be reduced by 30%. Thus, the impact

on human health and environment will decrease considerably. On the other hand, the costs

of waste management will increase significantly: While Izmir municipality spends now 14

€/capita&year for solid waste management, the most economic scenario of biological

treatment will cost an additional 21.- €/capita&year, increasing todays waste management

costs by 150%. For effective waste management decision support, it is recommended to

repeat this scenario analysis with a comprehensive and validated data set.

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1 Introduction

Municipal solid waste problem is a major concern, especially for large cities in Turkey

such as Izmir. The main solid waste disposal method in a number of cities in Turkey has been

unsanitary landfilling or open dumping, including Izmir.

According to the Turkish Law of Metropolitan Municipalities municipalities are

responsible for arranging solid waste management plans, and providing facilities of source

collection, transportation and recovery of the municipal, industrial, and medical wastes

(Official Gazette, 2004). However, the collection and transportation stages of solid waste

management are well organized in Izmir, while disposal of the collected waste is in a worse

situation. Municipalitiy of Izmir prefers landfilling as a disposal method due to their low cost

and simplicity. It creates secondary pollutions such as water pollution by leachate,

uncontrolled atmospheric emissions of landfill gases, bad odors and dust formation.

Untreated leachates are discharged directly into the Gulf of Izmir and they can permeate

underground water, also. Leachates contribute to the pollution of soil, underground water and

surface water, furthermore, leachates may cause malodors and aerosols.

Anaerobic decomposition of MSW in landfills generates anthropogenic greenhouses

gases which are about 40-60% methane and 40-50% carbon dioxide. This generation from

landfill sites has drawn attention due to their significant contribution to global warming.

Landfill areas cause not only environmental problems but also threat public health.

Biodegradation in landfill sites last over 100 years. Landfill sites are a heritage to our children

from us. For this reason, next generations have to cope with the problems stemming from

landfill sites.

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Izmir is a large metropolitan city of Turkey in the western Anatolia. It is located in the

Aegean Region of Turkey. Aegean Sea is to the west of the city and it has a big gulf called

Gulf of Izmir. Izmir has an area of about 11,973 km2 and the population of it is 4.050.028. It

consists of 28 townships. 91% of the population lives in the province and districts centers,

while 9% of population lives in the villages (Turkstat 2010).

According to the Prime Ministry Turkish Statistical Institute database 2010, the amount

of municipal solid waste (MSW) per capita in Izmir was found as 1.28 kg/ca.d. Approximately

5130 tons/day of municipal solid waste is generated in Izmir. Harmandalı Solid Waste Landfill

Area has been under service since 1992, which is operated by the Izmir Metropolitan

Municipality. At this site, more than 32 million tons waste has been landfilled until now.

Increasing population, rapid economic growth, the rise of living standards and immigration

will accelerate the future solid waste generation rate in Izmir. According to the Prime Ministry

Turkish Statistical Institute database 2013, it is expected that the total population of Izmir will

be 4,405,279 in 2023. According to this data, approximately 20 million tons waste will be

disposed of in the next decades. Today, the Harmandali landfill site is nearly completed its

capacity. Disposal sites failed to catch up with the increasing volume of waste. It is difficult to

find new landfill area. While Izmir municipality looks for a new area, they try to find some

alternative solid waste management systems. Due to these disadvantages of landfilling,

alternative uses of MSW such as composting, digestion, recycling must be implemented in

Izmir.

Approximately 46% of the total MSW was organic waste, amounting to about 2360

tons/day. Paper comprised 12% of the MSW at 618 tons/day. The quantities of plastic, glass,

metal, inert and other materials were 618, 206, 155 and 1184 tons per day, respectively.

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MSW components of Izmir have been composed of energy-rich biodegradable residuals such

as organic waste.

Uzundere and Menemen Composting Plants were active a short while ago, but they

became inactive due to operational problems such as high cost and low quality of the

compost produced. According to findings, it is expected that 9,2 million tones of organic

waste will be generated in Izmir until 2023. Due to huge amount of organic waste,

composting plants and anaerobic digestion plants should be constructed. In this way, volume

of landfill site, cost of transportation fuels, production of toxic leachate, gas emissions will be

decreased and the loss of valuable material will be prevented, as well. It is estimated that in

the year 2012, approximately 200 million m3 of methane has been emitted from the landfill

site and in the year 2023, emissions will reach to 240 million m3. Implemention of organic

waste disposal methods prevent not also serious environmental problems but also conserve

resources.

In order to solve these problems, the integrated municipal waste management system

and an effective biological treatment method will be determined based on the methodology of

material and substance flow analysis.

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2 Aim of Study and Research Questions

The aim of this study is to compare various scenarios for integrated waste management

based on biological waste treatment and the methodology of material flow analysis that was

introduced by Baccini & Brunner (1991).

Integrated waste management has been defined as the integration of waste streams,

collection and treatment methods, environmental benefit, economic optimisation and societal

acceptability into a practical system for any region.

In the past 20 years, as the economy has achieved faster growth, ecological damage

and environmental pollution have increased at a high rate.

An integrated solid waste management (ISWM) system which includes the reducing,

reusing, recycling and disposal of waste material is considered to be an optimized waste

management system where the environmentally and economically best solution is chosen for

each case, without regard to the waste hierarchy.

As shown in Figure1, there were a lot of changes in the strategies of solid waste

management in the advanced industrial countries during the period of 1960-2004. One

revolutionary change was that the solid waste management begins with reduction-using less

to begin with and reusing more- and recycling. In addition, incinerating and composting

organic waste became dominant methods of solid waste treatment instead of disposal by

landfills (Hui, Y. et al, 2006).

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Figure 1. Solid waste management- revolutionary changes in the strategies in the advanced

industrial countries during the period 1960-2004 (Hui, Y. et al, 2006).

EU has firm principles upon which its approach to waste management is based.

• prevention principle – waste production must be minimised and avoided where

possible

• producer responsibility and polluter pays principle- those who produce the waste

or contaminate the environment should pay the full costs of their actions

• precautionary principle- we should anticipate potential problems

• proximity principle- waste should be disposed of as closely as possible to where

it is produced (Strange, K., 2002).

These principles are made more concrete in the 1996 EU general strategy on waste

which sets out a preferred hierarchy of waste management operations

• prevention of waste

• recycling and reuse

• optimum final disposal and improved monitoring (Strange, K., 2002)

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These countries are centered on a broadly accepted “hierarchy of waste management”

(Figure 1) which gives a priority listing of the waste management options available. Several

variations of the hierarchy are currently in circulation, but they are essentially similar.

The hierarchy has little scientific or technical basis. It has a little use when a

combination of options is used in ISWM system. In ISWM system, the hierarchy can not

predict, for example, whether composting combined with incineration would be preferable to

recycling combined landfilling. The hierarchy can not provide an assessment of ISWM system

and does not address costs. If prevention is the most economic way of reaching a particular

waste management objective, then this method should be chosen. If the disposal option is

more economic, the waste hierarchy should not be used to justify avoiding this choice.

Neither is a “waste hierarchy” approach needed such as “prevention before recycling and

disposal” (Brunner, P.H., et al., 2012).

Integrated waste management starts with collection and sorting, implies the use of a

range of different treatment and disposal options such as recycling, composting and

anaerobic digestion, incineration, landfill and alternative options such as pyrolysis,

gasification, composting and anaerobic digestion and waste reduction, re-use.

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Figure 2. The Elements of Integrated Waste Management

However, integration also implies that no one option of treatment and disposal is better

than another, but that the overall waste management system is the best environmentally and

economically sustainable one for a particular region. Environmental sustainability means to

reduce overall environmental impacts of waste management, including energy consumption,

pollution of land, air and water. Economic sustainability means that the overall costs of the

waste management system should operate at a cost level acceptable to all areas of the

community, including householders, businesses, institutions and government (White et al

1995; Warmer Bulletin 49, 1996).

While designing integrated waste management system, the following goals have been

adopted for integrated solid waste management:

• Protection of mankind and the environment.

• Conservation of resources such as materials, energy, land and biodiversity

• Aftercare-free waste treatment system (e.g., landfills)

• Find solution at the least cost

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The municipal solid waste are composed of energy-rich biodegradable residuals, such

kitchen waste which includes vegetables, fruits and cooked and processed food. In Izmir,

1.87 million tons of waste were generated in 2010 of which organic waste refuse accounted

for 46%. Anaerobic digestion (AD) of KW is regarded as an attractive option due to its

environmental and economical benefits. Firstly, the main solid waste management system

was established and then three different biological treatment scenerios were investigated and

compared with one another regarding to these goals. Construction waste and industrial waste

materials were not considered.

Objectives and Research Questions

The goal of this study is to support the decision-maker on investment in waste management

system in Izmir. It is important that the cost of waste treatment will be affordable according to

its budget and it must reduce the direct impacts of environmental impact.

Currently, MSW is dumped directly on a landfill site. Direct landfilling pollutes to ground water

and soil, releases emissions and greenhouse gases to atmosphere, causes many risks for

public health, leads to loss of valuable material. Landfill site needs huge volume and land.

Harmandali landfill site has an area of 900.000m2. In this study, a cost analysis will illustrate

current and scenarios costs and will help to decide biological treatment method.

In order to reach the goal of the study, the following major research questions have to

be answered: How much of organic fraction of MSW is there in the MSW of Izmir? How much

of wastes do go to biological treatment plant? What is the recycling ratio and disposal ratio?

How much does it cost to treat organic wastes? The costs include the investment cost,

operational costs and depreciation costs.

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3 Methodology of Material and Substance Flow Analysis

Material flow analysis (MFA) is a systematic assessment of the flows and stocks of

materials within a system defined in space and time. Because of the law of the conservation

of matter, the results of an MFA can be controlled by a simple material balance comparing all

inputs, stocks and outputs of of a process (Brunner, P.H., 2004).

It has to be known that knowledge of the material flows into, out from and within all

processes in the waste management system to reach effective waste management.

The main purpose of waste management is separation and transformation or

accumulation of substances, either by logistics (separate collection) or by chemical and

mechanical technologies (thermal, separation and size reduction). An appropriate waste

management strategy for reaching the objectives is to establish “clean cycles” (treatment)

and direct remaining materials to safe “final sinks”. The main elements of such a system are

collection, treatment and final disposal (Brunner, P.H., et al., 2012). An MFA consists of

several steps that are;

• System definition in Space (Izmir) and Time (year)

• Determine system boundry

• Determine waste generation rates (the ratio of mass per time- kg/day, tons/day, etc.)

and waste composition, substance concentrations (g/kg)

• Data uncertainties and reconciliation of data

• Determine transfer coefficients

• Establish a mass balance of materials for each process; inputs, outputs, stocks

• Establish a mass balance of substances for each material

• Calculate cost of processes

• Evaluate results

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4 Process Description

4.1 Theory and Technology of Composting

Theory of composting and effecting parameters of composting process

Composting is a microbial aerobic transformation and stabilization of heterogeneous

organic matters in aerobic conditions and in solid state (Stentiford, E. et al, 2010). Aerobic

microorganisms extract energy from the organic matter through a series of exothermic

reactions that break the material down to simpler materials. The basic aerobic decay

equation is;

[complex organics] + O₂(aerobic microorganisms)→ CO₂ + H₂O + NO₃ˉ + SO₄ˉ2 + [other less

complex organics] + [heat]

MSW composting results in a volume reduction of up to 50 percent and consumes

about 50 percent of the organic mass on a dry weight basis, by releasing mainly CO₂ and

water (Diaz, L.F. et al, 2007).

Temperature

The water and aeration are the significant factor to be controlled during composting.

The process is exothermic and energy is released. A part of this energy is used by

microorganisms and the rest of energy is lost in the form of heat. This heat can produce a

temperature increase in the mass. Temperature reaches and exceeds 70-90°C. Indeed, high

temperatures inhibit microbial growth, causes slowing the biodegradation of organic matter.

Temperature effects microbial metabolic rates and population structure. To have a maximum

microbial diversity, the temperature must range between 25 and 45°C; to have the highest

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rate of biodegradation, the temperature must range between 45 and 55°C. Bacteria,

actinomycetes and fungi are the main microbial biomass during composting process. If the

temperature is below 20°C, microbial activity is low. When the temperature is above 55°C,

the highest rate of pathogen inactivation can be obtained. In large composting masses,

temperatures do not exceed about 80°C, which is also the temperature at which biological

activity effectively stops (Palmisano, A.C. et al., 1996).

Composting progresses through a sequence of stages. The first stage of composting

process is mesophilic phase in which temperatures rise from ambient temperature to 45°C.

Within a few days, second phase of composting (thermophilic phase) starts and the

temperature can easily reach and exceed 70°C. This phase is limited in terms of temperature

and exposure time to obtain a balance between high stabilization rates and good sanitization,

often to satisfy local legistation regarding sanitization conditions (Stentiford, E. et al., 2010).

During the third phase, the amount of easily decomposable materials declines, maturation

stage starts. The temperature drops from around 50°C to ambient.

Moisture content

Water is essential for all microbial activity. The moisture contents of MSW, organic

waste and garden waste vary between 60-75%, 55-75% and 45- 65%, respectively. Average

moisture content of MSW is 65-80% in Turkey (Melikoglu, M., 2012). All microbial activity

ceases when the moisture content is less than 8-12% (Diaz, L.F. et al., 2007). At the end of

the composting process, the finished compost should not have a moisture content greater

than 35-45% to avoid storage, transport and handling problems and to prevent any further

biological activity in the stabilized compost. Compost with a moisture content lower than 35-

45% may increase the release of dust (Krogmann, U. et al., 2010). Optimal moisture content

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in the incoming waste varies and depends on the physical state and size of the particles.

Normally, a 60% moisture content in the incoming waste should be satisfactory. It is

estimated that moisture content of organic waste varies 60% in Izmir.

Aeration, Particle Size, Oxygen Content

Regardless of the feedstock or the selected technology, a minimum free space of 20-

30% is recommended for a sufficient supply of oxygen to the waste (Krogmann, U. et al.,

2010). Grinding and shredding reduce particle size and porosity but enhance degradation

rate owing to increase surface area of total mass. There is a minimum size below which it is

exceedingly difficult to maintain an adequate porosity in a composting mass. This size is the

“minimum particle size” of the waste material. It is suggested that particle size of organic

waste can be bigger than 2.5-5.0 cm.

Oxygen is a key element in the composting. The carbon dioxide content gradually

increases and the oxygen level falls. The average CO2 plus O2 content inside the mass is

about 20%. Oxygen concentration varies from 15 to 20% and carbon dioxide from 0.5 to 5%.

When the oxygen level falls below this range, anaerobic microorganisms begin to exceed

aerobic ones. Fermentation and anaerobic respiration processes take over. A lack of oxygen

is common reason for composting failures (Palmasino, A.C., 1996). Therefore, it is important

to supply oxygen to the mass of organic waste. In the windrow composting facilities, turning

of windrows provides oxygen up-take.

C/N and pH

Biodegradable wastes generally contain enough macronutrients and micronutrients to

sustain the composting process. The macronutrients for microbes are (C), nitrogen (N),

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phosphorous (P), and potassium (K). The micronutrients are cobalt (Co), magnese (Mn),

magnesium (Mg), copper (Cu), and a number of other elements. Calcium (Ca) falls between

the macro and the micronutrients.

The optimum C/N ratio for most types of wastes is about 25-30. Wastes with a lower or

higher C/N can be composted, but too high C/N slows down the microbial degradation and

too low C/N results in the release of nitrogen as ammonia. If a compost has a high C/N and

decomposes rapidly in the soil, it can rob the soil of the nitrogen needed to support plant

growth. If the compost has a too low C/N, the ammonia released can be phytotoxic to plant

roots (Zucconi et al, 1981).

The optimum pH range is between 7 and 8. During composting the pH increases due

to the degradation and volatilization of organic acids. If anaerobic conditions prevail during

composting, pH decreases in biomass owing to organic acids produced as anaerobic

intermediate products.

Technological process factors of windrow composting

Windrow composting can be constructed for Izmir. Because windrow composting is the

simplest and the cheapest technology. Windrows are naturally ventilated as a result of

diffusion and convection. They are aerated by forced or vacuum –induced aeration.

During composting, three particular features can serve as useful indicators for

monitoring the performance of a compost process. They are: (1) temperature rise and fall; (2)

biodegradation of organic material - destruction of volatile solids; (3) change in odor and

appearance.

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The degradation of organic matter during composting, measured as the percentage of

the initial mass of volatile solids that is lost and the length of the composting period including

curing. In a typical composting facility, food wastes are degraded more than 60%, biowaste

(source separated food and yard waste) about 50% and lignocellulytic plant materials about

35-45% (Krogmann, 1994).

The optimum temperature during the high-rate decomposition period is about 40-55°C.

Within this temperature interval, high rate of stabilization is obtained. At temperatures over

60°C, the diversity of the microorganisms is greatly reduced. At 70°C the total biological

activity is 10-15% less than the one at 60°C, whereas, at 75-80°C, no significant biological

activity is detected (Krogmann, U. et al., 2010). In order to obtain a high rate of sanitization,

the temperature in the mass of windrow must range from 55-70°C (Stentiford, E. et al., 2010).

The elevated temperatures destroy most of the pathogenic bacterium, eggs and cysts. Some

of the more common pathogens and their survival at elevated temperatures are shown in

Table 1. The product of thermophilic composting is essentially free of pathogens.

During curing, the optimum temperature is around 40°C. If the supply of easily

decomposable material is depleted, the maturation phase begins. Temperature begins to

decline, persists until ambient temperature is reached. Reduction of the concentration of

volatile solids is a indicator of the stabilization of compost. Some of the early methods

proposed for determining stability were the following: final drop in temperature (Golueke and

McGauhey, 1953); degree of self-heating capacity (Niese, 1963); amount of decomposable

and resistant organic matter in the material (Rolle and Orsanic, 1964); oxygen uptake

(Schulze, 1964); growth of the fungus Chaetomium gracilis (Obrist, 1965); and the starch test

(Lossin, 1970). In the United States, pathogen reduction regulations require temperatures

above 55°C for 15 days and five turnings during this time in windrow facilities (US EPA,

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1993). In Germany, pathogen reduction regulations require temperatures above 55°C for 14

days or above 65°C in open and above 60°C in in-vessel facilities for 7 days (German

Federal Government, 1998). The main difficulty is to ensure that all particles are achieved to

the desired temperature.

Table 1. Destruction of Some Common Pathogens and Parasites during Composting

(Vesilind, P.A., 2010)

Salmonella typhosa No growth beyond 46ºC; death within 30 min at 55-60ºC and within 20 minutes at 60ºC; destroyed in a short time in compost environment

Salmonelia sp Death within 1h at 55ºC and within 15-20 min at 60ºC

Escherichia coli Death for most within 1h at 55ºC and within 15-20 min at 60ºC

Shigella sp. Death in 1 h at 55ºC

Entamoeba histolytica cysts Death within a few minutes at 45ºC

Trichinella spiralis larvae Quickly killed at 55ºC

Brucella abortus or Br. Suis Death within 3 min at 62ºC and within 1 h at 55ºC

Streptococcus pyogenes Death within 10 min at 50ºC

Mycobacterium tuberculosis var. Hominis

Death within 15-20 min at 66ºC or after momentary heating at 67ºC

Corynebacterium diphtheriae Death within 45 min at 55ºC

Ascaris lumbricoides eggs Death in less than 1 h at 50ºC

The attainment of a dark color or an earthy odor is not an indication, because these

characteristics may be acquired long before stability is reached. Reaching a C/N lower than

20/1 also is not indicative. For example the C/N of raw manures may be lower than 20/1.

Dryness should not be confused with stability either. It is true that if the moisture content is

lower than 15-20%, microbial activity is minimal (Palmasino, A.C., 1996).

Aeration is one of the most important factors of composting process. Aeration is

provided by turning of windrow with windrow turner. When the windrows are turned, both their

porosity increases and homogenize compost, moisture -temperature gradients are balanced

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in the mass of windrow, also. If the windrow is turned constantly, the effect of turning on the

oxygen uptake could be more efficient.

There is a relationship between turning frequency of composting and some

physicochemical parameters that may serve as compost maturity indicators (CCQC, 2001).

Turning frequency effects rate of decomposition as well as compost quality. Turning affects

moisture content, dry matter, pH, total carbon, total nitrogen, C/N ratio and temperature of

composting piles (Getahun, T. et al., 2012). As the turning frequency increases, carbon

content of compost, nitrogen content of compost and C/N ratio decrease within the

composting mass. It leads to lower plant growth. However, excessive aeration causes to

decrease temperature and moisture content of material.

A higher turning frequency leads to a decrease in retention time and less investment

cost and an increase in operating cost. For example, the retention time to produce a

“stabilized compost” made from leaves, grass clippings and brush was reduced from 4-5

months to 2-3 months when the turning frequency was increased from once per month to

seven times per month (Micheal et al., 1996).

High turning frequency requires labor-intensive management and causes high cost.

After high rate degradation phase, generally turning is not made due to high cost. Turning

frequency decreases from high-rate degradation to curing (Krogmann, U. et al., 2010). For

frequently turned, naturally ventilated windrows of biowaste, retention times of 12-20 weeks

are reported (Kern, 1991), while for windrows of yard waste 12-72 weeks are found.

(Krogmann, U. et al., 2010). In order to prevent the lack of moisture which inhibites

composting, moisture content of windrows should be adjusted to 50-60% by sprinkling water.

It is recommended that the moisture content should not fall below 35-40%, but at the end of

process, the moisture content should be 35-40% in the stabilized compost.

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To sum up, biodegradation rate depends on temperature, retention time, turning

frequency, transfer coefficients classified according to composting types.

On Table 2, amount of volatile solids losses and reaction rate constants are given with

operation conditions of some composting facilities in Europe. According to these data, volatile

solids losses range from 29%-66%, whereas Adani et al.(2000) obtained a value of 50% and

Fricke and Muller (1999) values that ranged from 34% to 68%(Baptista,M., 2010). The low

VS consumption values (29% and 32%) were an indication that process management in

these plants was poor (Baptista,M., 2010). The avarage of the rest of the VS loss data on the

table is 59.5. Thus, the volatile solid loss can be estimated as 60%.

First-order rate constants presented in the literature. For example, Mason (2006) and

Mason (2008a) reported values in the ranges 0.0181-0.0749 d-1 and 0.02-0.41d-1 respectively

(Baptista M., 2010).

On the other hand, using first order kinetic equation (1), the VS losses can be calculated

for different retention times (Table 3-4). On the Table 2, first order rate constants range from

0.035 to 0.29. Between the these reaction rates, amounts of volatile solid losses were

calculated using equation (2).

VS (consumed)= VS(initial) x (1- e-kxt) (1)

VS (incoming waste) = 0.70

VS (the fast degrading volatile solids) =0.35

VS (the slow degrading volatile solids) =0.35

kf = fast reaction rate

ks = slow reaction rate

VS (consumed)= 0.70-(0,35 e-kfxt +0,35e-ksxt) (2)

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Table 2. Volatile Solids loses and Reaction Rates

Material System description Study scale

Residence time (day)

VS loss

(%)

k k (fast+slow-calculated)

Source

Scottish MSW treated in a rotating drum for 6 h, then sieved at 50mm

Static pile with hybrid aeration system, one mixing over the 51 d; 10 tons test

Pilot 51 61 0,27+0.01 Sesay et al.(1998)

Italian MSW treated mechanically; fraction ˂50mm

First 37 day- continually aerated windrow; turning every 2 days; then curing phase

First 37day- composting in a 150l adiabatic reactor with forced aeration; then 79 d in a non-ventilated heap, turned every 4-5 d; with water addition; 26 kg sample

Full

Lab

37+79

37+79

57

66

0,29+0.01

0,27+0.01

Adani et al.(2000)

French MSW Windrow with positive forced aeration; 37.5 tons test

Pilot 175 62 0,25+0.01 Lornage et al.(2007)

Portugal MSW Positive aerated windrows; closed building; turning frequency :6.3 (d)

150,000 ton/year

63 29 0.05-0.084 Baptista, M. et al. (2010)

Portugal MSW Negative aerated windrows; closed building; turning frequency :7(d)

160,000

ton/year

49 32 0.035-0.052

Baptista, M. et al. (2010)

Portugal MSW Negative aerated windrows; closed building; turning frequency :7(d)

50,000

ton/year

59.5 52 0.064-0.114

Baptista, M. et al. (2010)

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It is estimated that the

fraction of the “fast” degrading

volatile solids is 35% and the

fraction of the “slow” degrading

volatile solids is 35% (Figure

3).

Figure 3. Fractions of volatile and non-volatile solids

Table 3. VS losses of different first order rate constants for different retention times.

kf (fast)

ks (slow)

VS loss % 30days (turning) +45

days (nonturning)


days (nonturning)


days (nonturning)

0.035 0.02 50 55 58.7

0.05 0.02 54 59 61.92

0.10 0.02 60 63 64.56

0.15 0.02 61.80 63.50 64.78

0.20 0.02 62.10 63.59 64.79

0.25 0.02 62.18 63.59 64.79

0.30 0.01 62.19 63.59 64.79

TU Vienna 23

Table 4. VS losses of different first order rate constants for different retention times

kf (fast)

ks (slow)

VS loss % 40 days (turning) +10

days (nonturning)


days (nonturning)


days (nonturning)

0.035 0.02 32.71 55 55.58

0.05 0.02 36.61 59 59.47

0.10 0.02 40.7 63 63.57.

0.15 0.02 41.25 63.50 64.12

0.20 0.02 41.33 63.59 64.20

0.25 0.02 41.34 63.59 64.21

0.30 0.01 41.34 63.59 64.21

On table 3/4, It is found that VS losses vary between 55% and 63.59% for 40 days

high rate composting, then curing 45 days. The retention time of composting plant can be 85

days, because VS losses are above 60%.

On Table 5, for windrow composting, transfer coefficients of compost, transfer

coefficients of losses are calculated and they are 66±7.6, 34± 7.6, respectively. For enclosed

composting, transfer coefficients of compost, transfer coefficients of losses are calculated

and they are 34±3, 66±6 respectively. For home composting, transfer coefficients of compost,

transfer coefficients of losses are calculated and they are 43±5, 57± 7, respectively. For in-

vessel composting, transfer coefficients of compost, transfer coefficients of losses are

calculated and they are 39±8, 60±8, respectively. Moreover, transfer coefficient can be

calculated using first order kinetic equation (3);

TU Vienna 24

Mt= M0x (fo+f1 e-k1xt +f2e-k2xt+………………+ fne-knxt) (3)

Mt= mass remaning time t

M0= initial mass =81.6 kg/ca.a

fn= fraction of mass with a reaction rate of kn

fo= non volatile fraction=0.30 (Figure 1)

f1 (fast) = the fast degrading volatile solids fraction=0.35 (Figure1)

f2 (fast) = the slow degrading volatile solids fraction=0.35 (Figure1)

kf: 0.15 (Table3-4)

ks: 0.02 (Mason(2006) and Mason (2008a))

Fast Degradation Phase ( First 40 days)

M40= 81.6x (0.3+0.35 e-0.15x40 +0.35e-0.02x40)=81.6x0.46=37.54 kg

TKcompost =46% and TKloss=%54

Curing (45 days)

M40=37.4x (0.72+0.28e-0.02x45)= 37.4x0.83=31.04 kg

TKcompost =38% and TKloss=62%

In this work, the transfer coefficient of composting is 62% for losses and is 38% for compost.

TU Vienna 25

Table 5. Classification of Transfer coefficient, moisture content, dry solid loss, processing time, frequency of mixing according to types of

composting

Types of wastes TK total TK

residue TK

compost TK

losses Moisture content

Dry solid Loss

compost (%) (%) (%) of compost

(%) (%)

Garden waste (Vienna 2013) 60 15 45 40 35--40 35--40 Windrow composting 6-9

weeks once a day Lobau composting plant

Garden waste (Vienna 2002) 44 13 31 56 35--40 35--40 Windrow composting 6-9

weeks once a day Bruuner, P.H., et al. Garden waste 74 11 63 26 30..5 30..5 Windrow composting Andersan, J.K., et al.

Mean ± SD 59 41

Mixed waste ( Damascus city-2003) 64 38 26 36 Windrow composting NA Brunner, P.H., et al.

Mixed waste 59 43 16 41 In-vessel + Windrow comp. NA Razvi and Gildersieve,

1992

OFMSW 77 0 77 23 Tunnel+windrow

composting 3 weeks M. Pognani et. Atl., 2012 Mean ± SD 66±7.6 34±7.6 Calculation (first order kinetics) 38 62 Food wastes 40 60 U. Krogmann, 1994 Biowaste 50 50 U. Krogmann, 1994 Organic waste + Garden waste 15 15 70 NA Enclosed composting 8 weeks NA Istanbul composting plant

Organic waste 37 63 Enclosed composting NA Boldrin, A., Christensen,

T.H. Mean ± SD 33.5±3.5 66.5±6.5

TU Vienna 26

To Table 5.


residue TK

compost TK losses Moisture content

Dry solid Loss


(%) (%) Mixed waste (Dhaka city- 2002) 19 54 27 Home composting Brunner, P.H., et al.

40%Garden+60% Food waste 47 53 72 56 Home composting 6

months Imperial College London

20%Garden+80% Food waste 37 63 77 63 Home composting 6

months Imperial College London 40%Garden+58% Food waste+2% Paper 45 55 71 60 Home composting

6 months Imperial College London

40%Garden+56% Food waste+4% Paper 42 58 72 66 Home composting


20%Garden+78% Food waste+2% Paper 38 62 75 62 Home composting


40%Garden+58% Food waste+2% Paper 53

47 70 53 Home composting

6 months

Imperial College London

100%Garden 58

42 68 40 Home composting 13

months


40%Garden+60% Food waste 45


months




months

Imperial College London 40%Garden+58% Food waste+2% Paper 43


13 months


40%Garden+56% Food waste+4% Paper 39


13 months




months




months


Organic waste 45

55 75 NA Home composting 1 year every week Andersan, J.K., et al.,

2011

Organic waste 35

65 73 NA Home composting 1 year every week Andersan, J.K., et al.,

2011

Organic waste 36

64 69 NA Home composting 1 year every 6th

week Andersan, J.K., et al.,

2011

Organic waste 27

73 71 NA Home composting 1 year every 6th

week Andersan, J.K., et al.,

2011

Organic waste 44

56 67 NA Home composting 1 year No Andersan, J.K., et al.,

2011

Organic waste 35

65 71 NA Home composting 1 year No Andersan, J.K., et al.,

2011 Mean ± SD 42.85±5.28 57.15±6.69 71.84±9.8 56.46±

TU Vienna 27

To Table 5.


residue TK

compost TK losses Moisture content

Dry solid Loss


(%) (%)

Organic waste 32 2

66

In-vessel composting NA Boldrin, A., Christensen,

T.H. Agricultural wastes

AGW-T01 49

51

In-vessel composting turning Adekunle, I.M.,2010 AGW-T02 47

53

In-vessel composting turning Adekunle, I.M.,2010

AGW-T03 46

54

In-vessel composting turning Adekunle, I.M.,2010 AGW-U01 36

64

In-vessel composting non-turning Adekunle, I.M.,2010

AGW-U02 38

62

In-vessel composting non-turning Adekunle, I.M.,2010 AGW-U03 34

66


Household wastes

HHW-T01 39

61


HHW-T02 41

59

In-vessel composting turning Adekunle, I.M.,2010 HHW-T03 50

50


HHW-U01 34

66

In-vessel composting non-turning Adekunle, I.M.,2010 HHW-U02 35

65


HHW-U03 36

64

In-vessel composting non-turning Adekunle, I.M.,2010 Municipal wastes

MSW-T01 47

53

In-vessel composting turning Adekunle, I.M.,2010 MSW-T02 42

58


MSW-T03 57

43

In-vessel composting turning Adekunle, I.M.,2010 MSW-U01 38

62


MSW-U02 39

61

In-vessel composting non-turning Adekunle, I.M.,2010 MSW-U03 35

65


Food waste 19

81 23 48 Horizontal bioreactor 90 days every two

weeks Zhang H. et al., 2010

Mean ± SD 39.7±7.90 60.2±7.92

SD,standard deviation; T-series, composts prepared with turning schedule; U-series, composts prepared without turning schedule

TU Vienna 28

4.2 Theory and Technology of Anaerobic Digestion

Theory of anaerobic digestion and effecting parameters of anaerobic digestion process

Anaerobic digestion of municipal solid waste is a controlled process of microbial

decompostion where, under anaerobic conditions, a consortium of microorganisms convert

organic matter into methane, carbon dioxide, inorganic nutrients, and humus (Palmisano,

A.C.,1996) (Figure 4). The anaerobic decomposition of organics can be described as

(Worrell, A.W., 2010);

[Complex organics] + heat → CO2 + CH4+ H2S + + NH+4

The overall anaerobic biological process involves several general pathways for

decomposition of organic complexes and compounds to methane and carbon dioxide. These

pathways are depolymerization, fermantation, acetogenesis and methanogenesis.

Depolymerization

Microorganisms hydrolyze polymeric (macromolecular) solid substrates into smaller

and dissolved molecules. This step is referred to as hydrolysis, also. Hydrolysis reactions are

fulfilled by extracellular enzymes called hydrolases which are esterases, glycosidases,

peptidases, lipases, lyases, etc. The products of depolymerization are soluble smaller

molecules, hereby, this step is also known as solubilization.

Different groups of fermentative bacteria are capable of excreting the extracellular

enzymes that are needed for the hydrolysis of complex polymeric compounds in the waste

into oligomers and monomers that can be taken up by the microorganisms. The proteleolytic

bacteria produce proteases that catalyze the hidrolysis of proteins into aminoacids. The

cellulytic and xylanolytic bacteria produce cellulases and/or xylanases that degrade cellulose

TU Vienna 29

and xylan (both are carbohydrates) to glucose and xylose, respectively. The lipolytic bacteria

produce lipases that degrade lipids (fat and oils) to glycerol and long-chain fatty acids

(Angelaki, I. et al., 2010).

Fermentation

During fermentation, sugars and amino acids are converted to volatile fatty acids

(VFA), alcohols, hydrogen and CO2, but long-chain fatty acids from the hydrolysis of lipids are

not converted. When the reactor is operating under stable conditions, most substrate is

converted to acetate and hydrogen directly. However, when the reactor is overloaded, either

excessive production of acetate and hydrogen, or pH extremes occur.

Acetogenesis

Acetogenesis is a linkage between the degredation into water-soluble compounds and

methane formation. Volatile fatty acids (VFAs) and alcohol are oxidized to acetate and H2.

This conversion can only take place at a low concentration of hydrogen (H₂), which is

produced during acetogenesis as a by-product. Hydrogen consuming methanogens which

convert H2 and CO2 to CH4 keep the concentration of H2 low. While acetogens produce H2,

methanogens consume H2. Thus, at the standard conditions, the balance is set up in the

biomass.

Methanogenesis

Methane is generated primarily by two pathways: Hydrogenotrophic methanogenesis,

which converts H2 and CO2 into CH4, and aceticlastic methanogenesis, which converts

acetate into CH4 and CO2. While hydrogenotrophic methanogenesis typically accounts for 60-

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70% of CH4, aceticlastic methanogenesis typically generates 60-70% of CH4. These

organisms are strict anaerobs and have very slow growth rates (Angelidaki, I. et al., 2010).

The main products of anaerobic digestion are biogas and digestate. The biogas from

organic compounds usually consist of 55-65% CH4 and 35-45% CO2. The biogas contains

also ammonia, H2S and numerous volatile organic compounds, which constitute only less

than 1% of the biogas (Angelidaki, I. et.al., 2010).Biogas yield for some types of waste are

given in Table 6.

The energy content of biogas is significant and it can be used directly for producing

electricity and heat or can be converted to a fuel oil.

Figure 4. Degradation steps of anaerobic digestion (Pesta, G., 2007)

TU Vienna 31

Table 6. Biogas yield recorded from anaerobic digestion of the solid organic waste (Khalid,

A., et al., 2011).

Substrate Methane yield (l/kg VS) Municipal solid waste 360

Fruit and vegetable wastes 420

Municipal solid waste 530

Fruit and vegetable waste and abattoir wastewater

850

Swine manure 337

Municipal solid waste 200

Food waste leachate 294

Rice straw 350

Maize silage and straw 312

Jatropha oil mill waste 422

Palm oil mill waste 610

Household waste 350

Lignin-rich organic waste 200

Swine manure and winery wastewater 348

Food waste 396

The overall performance of the anaerobic digestion process depends on several process

factors which are temperature, nutrient balance, pH, retention time.

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Temperature

Temperature has a strong influence on both biodegradation rate and biogas

production. The change of rate constans regarding the temperature is given on Table 7.

Viscosity decreases and diffusivity increases with increasing temperature. It effects gas-liquid

equilibrium, also. Gases are less soluble at higher temperature, therefore as the temperature

is increased, the more gas is transferred to the gas phase. While within temperature ranges

from 40-60 °C, termophilic bacteria prevail in the digester, mesophilic bacteria prevail within

the 25-40°C temperatures. It has been observed that higher temperatures in the thermophilic

range reduce the required retention time.

Table 7. Rate Constants, k, for Gas Production in Anaerobic Digesters (Worrell, W.A., et al.,

2010)

Rate constant ( day-1)

Temperature, °C Initial Final

35 0.055 0.003 40 0.084 0.043 45 0.052 0.007 50 0.117 0.030 55 0.623 0.042 60 0.990 0.040

Source: Pfeffer, J.T. 1974. “Temperature Effects on Anaerobic Fermentation of Domestic

Refuse” Biotechnology and Bioengineering 16: 771-787. Copyright © 1974, John Wiley and

Sons.

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Nutrient Balance

Substrate composition is a major factor affecting the methane yield and methane

production rates. Table 6 shows the specific biogas yields and qualities of carbohydrates,

lipids and proteins. Due to the composition of the biodegradable organic compounds such as

lipids and proteins, a higher percentage of methane is produced, compared to oxidized

compounds like sugars.

Microorganisms utilize carbon during anaerobic digestion 20 to 30 times faster than

nitrogen. This predicts an optimal ratio from C to N of 20-30:1 within the substrate. For an

effective biogas process a ratio of at least 35-40 is required (Pesta, G., 2007).

pH

One of the most important environmental requirements is the proper pH. Easily degradable

substrate tend to acidify rapidly and the pH lowers noticeably. Methane bacterium are

inhibited when the pH falls below 6.2.

The pH in an anaerobic digester initially will decrease with the production of volatile acids.

However, as methane-forming bacteria consumes the volatile acids and alkalinity is

produced, the pH of the digester increases and then stabilizes.

Retention Time

The required retention time for completion of the AD reactions varies with differing

technologies process temperature. and waste composition. The retention time for wastes

treated in mesophilic digester range from 10 to 40 days (Pesta, G., 2007).

TU Vienna 34

Technological process factors of anaerobic digestion

There are the great diversity of reactor designs because of large variability of waste

composition and operational parameters (retention time, solids content, mixing, recirculation,

inoculation, number of stages, temperature). The discussion and evaluation of reactor

designs will greatly vary depending on whether one takes a biological, technical, economical,

or environmental viewpoint.

The commercial options for anaerobic digestion can be classified according to the

solids content in the reactor. When the digestion process contains 10-15% solids, it is

considered wet and the biomass in the digester looks like a liquid. But, when the digestion

process contains 20-40% solids, it is considered dry and the biomass in the digester looks

like a thick slurry. These systems can be one stage, two stages or batch facilities. A two-

stage digesters separete digestion process into two steps. In the first step, hydrolysis,

acidification and liquefaction take place, acetate, hydrogen and carbon dioxide are

transformed into methane in the second step. In two or multi-stage systems, the reactions

take place sequentially in the at least two reactors.

The digestion systems can be classified according to the temperature at which the

process is conducted. During mesophilic digestion, the temperature in the digestion keeps

around 35°C and during thermophilic digestion, the temperature in the digestion keeps above

50°C. Advantages and disadvantages of various anaerobic digestion systems have been

summarized on Table 8.

TU Vienna 35

Table 8. Advantages and Disadvantages of Various Anaerobic Digestion Systems. (Vandevivere P., et al., 2010).

Criteria Advantages Disadvantages Single- Stage Wet Systems

Technical Derived from well developed waste-water treatment technology Simplified material handling and mixing

Short-circuiting Sink and float phases Abrasion with sand Complicated pre-treatment

Biological Dilution of inhibitors with fresh water

Sensetive to shock as inhibitors spread immediately in reactor VS lost with removal of insert fraction in pre-treatment

Economic and Environmental

Less expensive material handling equipment

High consumption of water and heat Larger tanks required

Single- Stage Dry Systems

Technical No moving parts inside reactor Robust (insert material and plastics need not be removed) No short-circuiting

Not appropriate for wet (TS˂5%) waste streams

Biological Less VS loss in pre-treatment Larger OLR ( high biomass) Limited dispersion of transient peak concentrations of inhibitors

Low dilution of inhitors with fresh water Less contact between microorganisms and substrate (without inoculation loop)

Two- Stage Systems

Technical Operational flexibility Complex design and material handling

Biological Higher loading rate Can tolerate fluctuations in loading rate and feed composition

Can be difficult to achieve true separation of hydrolysis from methanogenesis


Higher throughput, smaller footprint

Larger capital investment

Batch Systems

Technical Simplified material handling Reduced pre-sorting and treatment

Compaction prevents percolation and leachate recycling

Biological Separation of hydrolysis and methanogenesis Higher rate and extent of digestion than landfill bioreactors

Variable gas production in single-reactor systems


Low cost Appropriate for landfills

Less complete degradation of organics (leach bed systems

TU Vienna 36

Single-stage wet system

The single-stage wet system had been inspired from technology in use for anaerobic

stabilization of biosolids (Figure 5). Both fresh and recycled process water are added to attain

10-15%TS. A pulper with three vertical auger mixers is used to shred, homogenize and dilute

wastes in sequential batches. The obtained slurry is then digested in large complete mix

reactors where the solids are kept in suspension by vertical impellers (Vandevivere P., et al.,

2010). Single-stage digesters are simple to design, build and operate. The methane yield in

one full-scale plant varied between 170 and 320 Nm3 CH4/kg VS fed (40 and 75 % VS

reduction) during the summer and winter months, respectively, as a result of the higher

proportion of garden waste during summer months (Saint-Joly et al., 1999).

Figure 5. Typical design of a single-stage “wet“system (Vandevivere P., et al., 2010).

TU Vienna 37

Single- stage “dry“ systems

In dry systems, the fermentation mass within the reactor is kept at a solids content in

the range 20-40% TS, so that only very dry substrates (˃ 50% TS) need be diluted with

process water (Oleszkiewicz and Poggi-Varoldo, 1997). The only pre-treatment is necessary

to remove the coarse impurities which are larger than ca. 40mm before feeding the wastes

into the reactor. Due to high viscosity, the biomass moves via plug flow inside the reactor.

This makes technical simplicity as no mechanical devices need to be installed within the

reactor for mixing. To guarantee adequate inoculation and mixing and to prevent local

overloading and acidification, there have been three designs: Dranco, Kompogas, Valorga

(Figure 6).

Figure 6. Different digester designs used in dry systems (A illustrates the Dranco design,

BRV designs, and C the Valorga design) (Vandevivere P., et al., 2000).

TU Vienna 38

In the Dranco process, the mixing occurs via recirculation of the wastes at the bottom

end. The total content of total solids ranges from 20 to 50%. The Kompogas process works

similarly, except that plug flow takes place horizontally. The horizontal plug flow is aided by

slowly-rotating impellers inside the reactors, which also serve for homogenization, degassing,

and resuspending heavier particles. The total content of total solids is around 23%.

The Valorga system is quite different in that the horizontal plug flow is circular in a

cylindrical reactor and mixing occurs via biogas injection at high pressure at the bottom of the

reactor every 15 minutes through a network of injectors (Fruteau de Laclos et al., 1997). This

elegant pneumatic mixing mode seems to work very satisfactorily since the digested wastes

leaving the reactor need not be recirculated to dilute the incoming wastes (Vandevivere P., et

al., 2000).

Two stage systems

Typically, two stages are used where the first one harbors the liquefaction-acidification

reactions, with a rate limited by the hydrolysis of cellulose, and the second one harbours the

acetogenesis and methanogenesis, with a rate limited by the slow microbial growth rate (Liu

and Ghosh, 1997; Palmowski and Müller, 1999). The main advantage of two-stage systems

is not only higher reaction rate, but also a greater biological reliability for wastes (Table3).

These systems provides adequate buffering and mixing of incoming wastes and controlled

feeding rate.

There are two types of two stage systems; with and without a biomass retention

scheme in the second stage (Figure 7 and Figure 8).

TU Vienna 39

Figure 7. The Schwarting-Uhde process, a two-stage “wet wet“ plug-flow system applicable

to source-sorted biowastes, finely-choped (ca. 1mm) and diluted and diluted to 12%TS

Vandevivere P., et al., 2000).

Figure 8. Two-stage“wet-wet“ design with a biomass retention scheme in the second stage

(BTA process). The non-hydrolyzed solids are not sent to the second stage (Vandevivere P.,

et al., 2000).

TU Vienna 40

In batch systems, digesters are filled once with wastes and then wastes are

transferred other degradation steps sequentially in the 'dry' mode, at 30-40 % TS. Though

batch systems seem like a landfill -in-a-box, they are run at higher temperatures and achieve

50- to 100-fold higher biogas production rates than that normally observed in landfills. Due to

continuously recirculation of leachate and the dispersion of inoculant, nutrients, and acids

(Figure 9).

Figure 9. Configuration of leachate recycle patterns in different batch systems

Single-stage anaerobic digestion can be constructed in Izmir. It is estimated that total

solid content of organic waste ranges from 30 to 40% in Izmir. In the dry systems, total solid

content is kept around 30-40%. That’s why, water usage will be small and there will be no

need for dewatering unit before composting process. On Table 7, biogas yield is given for

different dry-anaerobic digestion technologies. As seen on table 4, the highest methane yield

was obtained in the dranco process. Therefore, the system can be operated under the

thermophilic conditions and the retention time can be determined as 21 days, like in the

dranco process.

TU Vienna 41

Table 9. Process parameters and biogas yields of thermophilic (50-56°C) anaerobic digestion

of OFMSW (Walker L.R. et al., 2011)

Process Capacity Waste Total Solids During AD HRT Biogas Yield

(%) (day) (m3/kg VS)

DiCOM 900 m3 Mechanically - sorted OFMSW 17 12 0.44

BTA 3,4 m3 Sourced - sorted (SS)OFMSW 6--16 12 0.39

DRANCO 56 m3 Organic household waste-no paper 30--35 15--21 0.45

KOMPOGAS 200 m3 Fruit, yard and vegetable waste 15--40 13 0.39

SEBAC 3x0,7 m3 OFMSW ( paper, yard, food waste) NA 21 0.34

Several data samples were gathered and they summarized on Table 8. For dry

anaerobic digestion systems, the mean of transfer coefficient of digestate, transfer coefficient

of losses were calculated and they were 89.89±3.23, 9.73±2.65, respectively.

After anaerobic process, digested material will be composted.

Mt= M0x (fO+f1 e-k1xt +f2e-k2xt+………………+ fne-knxt) (3)

Mt= mass remaning time t

M0= initial mass =73.44 kg/ca.a

fn = fraction of mass with a reaction rate of kn

fo = non-volatile fraction=0.30 (Figure 1)

f1 (fast) = the fast degrading volatile solids fraction=0.35 (Figure1)

f2 (fast) = the slow degrading volatile solids fraction=0.35 (Figure1)

kf : 0.15 (Table3a-3b)

ks: 0.05 (Table3a-3b)

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Table 10. Transfer coefficients according to types of digesters and input, output values.

Types of wastes Input Digestate CH4+CO2 Storage

Total condensed TK(D)

TK (Losses) TK Average VS Vs

Types of Anaerobic digestion Reference

moisture

stock CH4/ CO2 CH4

CO2 degraded reduction

w.w.

(Mg /y) w.w.

(Mg /y) w.w.

(Mg /y) w.w. (%) (%) (%) (%) (%) (%) w.w.

(Mg /y) (%)

OFMSW 1860 (kg)

1730 (kg)

130 (kg) 93,00 7,00 60 35

Dry TS: 25%-termophilic-single phase- 14 days

Karena Ostrem, 2004

OFMSW

92-94 6--8

Dry-termophilic-single

phase- 14 days R. Stegmann,

2005

OFMSW 197(t) 177(t) 20(t)

90 10

40

Dry (TS:30%)-termophilic-single phase- 14 days Walker, L.R. et al.

SS-OFMSW 5426,504 (kg)

4577421 (kg)

726,650 (kg)

122,433 (kg) 12,526 (kg) 84,35 13,4 2,25 62.6 37.4

75

Dry (TS:28%)-termophilic-single phase- 21 days

Banks, C.J. et al., 2010

SS-OFMSW

84 16

Dry (TS:28%)-termophilic-single phase- 22 days

Pognani, M. et.al., 2011

SS-OFMSW

92 8

Dry conditions- TS

˃20% - 22 days Kranert and

Hillebrecht, 2000

Mean± DRY 89.89 ±3.23

9.73 ±2.65

OFMSW 86 14 Kompogas Kranert and

Hillebrecht, 2000

OFMSW

82 18

Dranco Sinclair and

Kelleher, 1995

OFMSW

81 19

Biocel Brummeler et al.,

1992 OFMSW

67 33

Subbor Vogt et al., 2002

Mean± DRY 85.23 ±7.44

14.54 ±7.1

OFMSW 45251 41294 3595

521 91,30 8,70

57±3

4022

Wet conditions- TS˂10%

Schievano, A. et al., 2011

Biowaste

94 6


Swine manure 38544 33418 5006

209 86,70 13,30

55±4

5249



Swine+cow+ 22745 20852 1594

253 91,70 8,30

63±4

2035



maize salige+

milk whey+ rice

TU Vienna 43

Fast Degradation Phase (First 30 days)

M40= 73.44x (0.3+0.35 e-0.15x30 +0.35e-0.05x30) = 73.44x0.38=27.90kg


Curing (20 days)

M40=27.90x (0.72+0.28e-0.05x20) =27.90x0.82=22.96kg


During compost + anaerobic digestion, the transfer coefficient of losses is 69% and the

transfer coefficient of mass is 31%.

TU Vienna 44

4.3 The Definition of Microwave Pretreatment

Microwaves are electromagnetic waves within a frequency band of 300 MHz to 300

GHz. In the electromagnetic spectrum (Fig.10), they are embedded between the radio

frequency range at lower frequencies and infrared and visible light at higher frequencies.

Thus, microwaves belong to the non-ionising radiations. But the microwave frequency range

is also used for telecommunications such as mobile phones and radar transmissions. In order

to prevent interference problems, special frequency bands are reserved for industrial,

scientific and medical (so-called ISM) applications, where a certain radiation level has to be

tolerated by other applications such as communication devices. In the range of microwaves

the ISM bands are located at 433MHz, 915 MHz and 2450MHz; the first is not commonly

used and the second is not generally permitted in continental Europe.

Outside the permitted frequency range, leakage is very restricted. Whereas 915 MHz

has some considerable advantages for industrial applications, for microwave ovens at home

the only frequency used is 2450 MHz. When the food is present inside the oven, the energy

of the electromagnetic waves is transferred to the water molecules, ions, and other food

components, raising the food temperature. Figure 11. shows two microwave ovens with

various components.

Figure 10. Electromagnetic spectrum (Datta, A.K., et., al., 2001).

TU Vienna 45

Figure 11. Schematic of two microwave oven systems used in some of the computational

studies presented here: (a) General Electric, Inc., Louisville, KY, (b) MDS 2000 Microwave

Digestion System, CEM Corporation, Matthews, NC. The rated power of the GE oven is 635

W and fort he CEM oven is 850W (Datta, A.K., et., al., 2001).

TU Vienna 46

The two key issues in microwave heating of food are (a) the magnitude of the energy

deposited by the microwaves and (b) the uniformity of the energy deposition. The magnitude

and uniformity are affected by both food and oven factors such as (Schubert, H, et.al, 2005):

i. Strength and distribution of electromagnetic fields where the food is placed

ii. Reflection of electromagnetic waves from the food, as characterized by its property

and geometry

iii. Propagation of the waves inside the foods, also characterized by the food properties

and geometry

The dielectric properties of most materials vary with several different factors. In

hygroscopic materials such as foods, the amount of water in the material is generally a

dominant factor. The dielectric properties also depend on the frequency of the applied

alternating electric field, the temperature of the material, and on the density, composition, and

structure of the material. In granular or particulate materials, the bulk density of the air

particle mixture is another factor that influences the dielectric properties. Of course, the

dielectric properties of materials are dependent on the chemical composition and especially

on the presence of mobile ions and the permanent dipole moments associated with water

and any other molecules making up the material of interest (Schubert, H, et.al, 2005).

In microwave processing, energy is supplied by an electromagnetic field directly to the

material. This results in rapid heating throughout the material thickness with reduced thermal

gradients. Volumetric heating can also reduce processing times and save energy. The

microwave field and the dielectric response of a material govern its ability to heat with

microwave energy. Microwave is thus an alternative method for conventional heating and can

give better results than classical thermal pretreatment. However, kinetics of methane

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production was increased; the time needed to reach the 80% value of ultimate volume of CH4

was reduced by 4.5 days (Jackowiak, D., 2010).

In microwave processing, energy is supplied by an electromagnetic field directly to the

material. This results in rapid heating throughout the material thickness with reduced thermal

gradients. Volumetric heating can also reduce processing times and save energy. The

microwave field and the dielectric response of a material govern its ability to heat with

microwave energy. Microwave is thus an alternative method for conventional heating and can

give better results than classical thermal pretreatment.

MW increases the kinetic energy of water dipoles bringing it to its boiling point very

quickly. Although the quantum energy of MW irradiation may not be strong enough to break

chemical bonds, some hydrogen bonded structures can be weakened or broken if exposed.

The direct interaction of MW irradiation of biological samples at the molecular or cellular level

is still poorly understood. Although no full scale studies using MW technology have been

reported for solubilization of organic suspended solids, it seems to be a promising option for

the treatment of numerous types of solid wastes. Due to its high moisture and suspended

organic solids content, KW is a suitable candidate for MW irradiation pretreatment. The Pre-

treatment helps to breakdown complex polymers into smaller molecules and promotes

hydrolysis the rate limiting step in AD of suspended organics. The yield of methane

production and volatile solids decomposition are increased during pretreatment process.

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5 Scenario Development and Definitions

Definitions of municipal solid waste (MSW) vary between countries. A working definition

is “wastes generated by households, and wastes of a similar nature generated by commercial

and industrial premises, by institutions such as schools, hospitals, care homes and prisons,

and from public spaces such as streets, markets, slaughter houses, public toilets, bus stops,

parks, and gardens”(Chaturverdi, B., 2010). This working definition includes most commercial

and business wastes as municipial solid waste, with the exception of industrial process and

other hazardous wastes. Different countries or cities define municipal solid waste rather

differently. So it is important to ask in each city what definition is. According to some experts

all industrial and construction and demolition (C&D) wastes should be included in the

definition of municipial solid waste.

First of all, the solid waste collection method used in Izmir is the mixed collection.

Sanitary landfilling is the only option that is currently used for the management of the MSW

(Figure 12. STAN/ Status Quo of Solid Waste Management in Izmir, 2010). All types of

wastes- municipal, industrial, medical and hazardous- are disposed in Harmandali Landfill

Site. The wastes from households, offices, restaurants, public facilities, industrial wastes and

sludge have been disposed separetely within different three lots in landfill site which has an

area of 170.000 m2 for domestic waste, 19.000 m2 for industrial, medical and hazardous

wastes, 24.000 m2 for sludge. Secondly, there is no source separation and recyclable wastes

which are approximately 15% of total municipial solid waste have been collected by

scavengers at the disposal bins for selling to informal collectors. As a result, approximately

15% of total municipial waste have been recycled at 70 kg / ca. year (Figure12).

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5.1 Status Quo of Solid Waste Management in Izmir

Figure 12. Status Quo of Solid Waste Management in Izmir, 2010

Izmir province consists of twenty eight municipalities: Bergama, Dikili, Kinik, Aliaga,

Foca, Menemen, Cigli Karsiyaka, Bornova, Konak, Balcova, Narlidere, Guzelbahce,

Gaziemir, Buca, Kemalpasa, Bayindir, Odemis, Kiraz, Beydag, Tire, Selcuk, Torbali,

Menderes, Seferihisar, Urla, Cesme, Karaburun. In some towns, unsanitary landfilling is

undertaken for the management of solid wastes. Due to the Law for Metropolitan

Municipalities, some of them started to close unsanitary landfill sites. Today, all types of

wastes- municipal, industrial, medical and hazardous- have been collected from twenty

townships and have been sent to Harmandali Landfill Site, amounting to about 467

kg/ca.year.

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Figure 13. Status Quo of Solid Waste Management in Izmir_ Subsystem of “Collection”, 2010

The solid waste collection method used in Izmir is the curb-side collection method.

Solid wastes are stored in containers, in sizes of 400 lt. or 800 lt. The dimensions and

numbers of containers vary according to the quantity of waste. It is estimated that 15% of

total generated wastes (Turkstat, 2010) which are recyclables; glass, paper, plastics, metals

has been collected by scavengers, approximately 70 kg/ca.a (Figure 13). Materials are then

recycled by specialized recycling companies. Before the trucks come, scavengers pick up

recyclables. The rest waste is transferred to transfer stations. Then bigger trucks deliver

larger amounts of waste to Harmandali Landfill Site which is 27 km away from city centre.

There are nine transfer stations in Izmir; Halkapinar, Karsiyaka, Foca, Gediz, Kisikkoy, Torbali

Gumuldur, Urla, Turkeli (Figure 14).

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Figure14. Transfer Stations in Izmir

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Main System of Solid Waste Management for Izmir

The main MFA system includes three typical processes: mechanical treatment,

biochemical treatment and thermal treatment and controlled final disposal option (Figure15.

STAN MFA Model_ Main system for Izmir, 2010).

To be able to obtain an effective waste management system, it is inevitable that MSW

have to be made on source separation. Waste sorting can occur manually at the household

and collected through curbside collection streams. Waste sorting means dividing waste into

dry and wet. Wet waste typically refers to food waste usually generated by eating

establishments, soiled food wrappers, hygiene products, yard waste, tissues and paper

towels and any other soiled items that would contaminate the recyclables. Dry waste includes

all recyclables that are paper, glass, plastics, electronic wastes, scrap metal and household

hazardous wastes. Izmir residents will store wastes in green bins for wet waste and blue bins

for dry waste.

After MSW are collected separately, they are delivered to mechanical treatment plants

via transfer stations. Eight more transfer stations will be constructed as seen Figure16.

During mechanical treatment process, recyclable materials are sorted manually at hand

picking stations or are separated mechanically. This process typically involves conveyors,

industrial magnets, eddy current separators, trommels, shredders. Mixed waste from

mechanical treatment plant are send to thermal treatment plant, residual dry waste are send

to landfill site and recyclables are send to recycling facilities. Wet waste are send to biological

thermal treatment plant.

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Figure 15. STAN MFA Model_ Main system for Izmir, 2010

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Figure 16. Transfer Stations in Izmir

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Figure17. STAN MFA Model _ Subsystem of “Collection”, 2010

In this study, three scenarios were developed for biological treatment process. In order

to assist decisionmaker, this study compares the costs and benefits arising from Scenario 1,

Scenario 2a and Scenario 2b. While scenario1 includes unique composting process, scenario

2a and scenario 2b consist of anaerobic digestion and composting processes, anaerobic

digestion with microwave pretreatment and composting processes.

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5.1.1 Scenario 1: Composting

Figure 18. STAN MFA Model _ Subsystem of “Scenario-1”, 2010

Procedures

I. Space and Time : Izmir, 2010

II. Boundries of MFA: Wastes have been collected from 28 townships in Izmir.

III. Assumptions, Collections of data :

• Temperature can be kept between 40-55°C for stabilization and between 55°C to 70°C

for sanitization.

• Moisture content should be kept around 60% during composting.

• During first phase, dry solid of waste includes 30% non-volatile solids (ash) and 70%

volatile solids.

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• During curing, dry solid of waste includes 72% non-volatile solids (ash) and 28%

volatile solids.

• Retention time and turning frequency

First 40 days high-rate composting- turned every week; then curing phase, 45 days.

IV. Transfer coefficients and reconciliation of data

Based the datas on Table 4, It is estimated that TKcompost and TKloss can be 38% and 62%,

respectively.

5.1.2 Scenario 2a: Anaerobic Digestion and Composting

Figure19. STAN MFA Model_ Subsystem “Scenario 2a“,2010

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Procedures




During Anaerobic Digestion

• Average moisture content of MSW is 65-80% in Turkey (Melikoglu, M., 2012). Thus,

total solid content ranges from 20% to 35%.

• Type of anaerobic digestion system is a single- stage “DRY“system.

• Digester will be operated in the termophilic phase.

• Retention time: 21 days

• Transfer coefficients:

TK (digested material): 89.89±3.23%

TK (biogas lost):9.73±2.65%

During Composting


• Moisture content must be 35-40% end of the composting duration.

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• Temperature can be kept between 40-55°C for stabilization and between the 55 to

70°C for sanitization.


volatile solids.


volatile solids.

• Retention time of composting : 50 days

• During compost + anaerobic digestion process, transfer coefficients:

TK (compost): 31%

TK (losses): 69%

5.1.3 Scenario 2b: Anaerobic Digestion with Microwave Pretreatment and Composting

Figure 20. STAN MFA Model_ Subsystem “Scenario 2b“, 2010

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Procedures




During Microwave Pretreatment

• Frequency of microwave: 2450 MHz

• Retention time: 30 minutes

• Heating: MW irradiation at 175 °C


TK (supertanant): 15%

TK (residues from pretreatment): 85%

During Anaerobic Digestion

• Type of anaerobic digestion system is a single- stage “WET“system.

• Digester will be operated in the termophilic phase.

• Retention time: 12 days


TK (digested material): 20%

TK (biogas lost): 80%

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During Composting


• Moisture content must be 35-40% end of the composting duration.

• Temperature can be kept between 40-55°C for stabilization and between the 55°C to

70°C for sanitization.


volatile solids.


volatile solids.

• Retention time and turning frequency

First 40 days high-rate composting- turned every week; then curing phase, 45 days.

• Transfer coefficients and reconciliation of data

Based the datas on Table 4, It is estimated that TKcompost and TKloss can be 38% and 62%,

respectively.

• During compost + anaerobic digestion process, transfer coefficients:

• TK (compost): 31%

TK (losses): 69%

Substance flow analysis were performed by means of the mass- balance model STAN, SFAs

have been performed for carbon and nitrogen for each scenario. Transfer coefficients was

calculated base on data from Christensen (2012) (Figure 21-22-23-24-25-26)

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Figure 21. STAN C Flow Analysis_ Subsystem of “Scenario-1”, 2010

Figure 22. STAN C Flow Analysis_ Subsystem of “Scenario-2a”, 2010

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Figure 23. C Flow Analysis_ Subsystem of “Scenario-2b”, 2010

Figure 24. STAN N Flow Analysis_ Subsystem of “Scenario-1”, 2010

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Figure 25. STAN N Flow Analysis_ Subsystem of “Scenario-2a”, 2010

Figure 26. STAN N Flow Analysis_ Subsystem of “Scenario-2b”, 2010

It is obtained that the least carbon and nitrogen emissions have been released into the

atmosphere in the first Scenario. Its contribution to global warming will be less than other

scenarios.

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6 Cost Analysis for all scenarios

The cost of initial capital invesment and operating costs are calculated using equations which

are given on Table 9.

Table 9. Approximate cost functions for MSW treatment facilities in Europe (Tsilemou K.,

et.al., 2006)

Type of facility

Suggested cost functions for

Initial capital investment (€)

Open-air composting Y= 4000 x W0.7

Anaerobic digestion Y= 35000 x W0.6 W: amount of waste

Scenario 1

The cost of composting plant

Amount of incoming wet waste to composting plant = 204 kg/ca. year (STAN Scenario-1)

204 kg/ca. year=0.5589 kg/ ca. day.

Population= 4,050,028 ca.

Design Capacity: 0.5589 x 365 x 4,050,028 =826,200 ton/year

Initial capital investment (€)=Y= 4000 x W0.7 =4000x (826,200)0.7 =55,500,000 €

Depreciation period: 20 years. Discount rate: 6 %

Depreciation cost: 66,600,000 €/ 20 years

Operational cost: Y= 20 €/ton (Tsilemou K., et.al., 2006)

Annual operating cost: 20 €/ton x 826,200 ton = 16,524,000 €/ year

Total operating cost: 16,524,000 €/ year x 20 year= 330,480,000 €/ year

Total cost: 55,500,000 + 66,600,000 + 330,480,000 = 452,580,000 €/ 20 year

Total cost/ capacity= 452,580,000 €/ 20 year x 826,200 ton =27.40 €/ton

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Scenario 2a -Anaerobic digestion

Design capacity of anaerobic digestion plant

Amount of incoming wet waste to digestion plant = 204 kg/ca. year (STAN Scenario-2a)



Design capacity: 0.5589 x 365 x 4,050,028 = 826,200 ton / year

Initial capital investment (€)=Y= 35,000 x W0.6 =35,000x (826,200)0.6= 124,260,000 €



Operational cost: 30 €/ton (Tsilemou K., et.al., 2006)


Total operating cost: 24,786,000 €/ year x 20 year=495,720,000 €/year

Total cost: 124,260,000 + 149,520,000 + 495,720,000 = 769,500,000 €/ 20 year

Total cost/ capacity= 769,500,000 €/ (20 year x 826,200 ton)=46,57 €/ton

Revenue from sales of energy: 10 € /ton

Anaerobic digestion capacity: 826,200 ton/year

Moisture content: 60%

The amount of dry solid: 826,200 x 0.40 = 330,480 ton/year

The amount of volatile solid: 231,336 ton/year

Volatile solid reduction: 40% Thus,

The amount of destroyed volatile solid production: 92,534 ton /year

Methane yield (m3/kg): 0.36

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Methane yield (m3): 92,534 ton/year x0.36 m3/kg x 103kg/ton= 33,312,240 m3CH4/year

One cubic metre of CH4 has a heating value of around 22,400 kilojoules/m3.

33,312,240m3CH4/year x 22,400 kilojoules/m3=7.4619x1011 kilojoules

7.4619x1011 kilojoules= 207,270,356 kwh

207,270,356 kwh x 4 cent= 8,290,815 €/year

8,290,815 €/year / 826,200 ton/year = 10 €

Net cost for anaerobic digestion process = 47.5-10 = 37.5 €/ton

Scenario 2a - Composting

Design capacity of composting plant

Amount of incoming wet waste to composting plant from anaerobic dig. plant = 183.6 kg/ca.

year (STAN Scenario-2a)

183.6 kg/ca. year=0. 50 kg/ ca.day.


Design Capacity: 0.50x 365 x 4,050,028=739,130 ton/ year

Initial capital investment (€) =Y= 4000 x W0.7 =4000 x (739,130)0.7 =51,306,000 €


Depreciation cost: 61,600,000 €/20 years




Total cost: 51,306,000 + 61,600,000 + 297,432,000 = 410,338,000 €/ 20 year

Total cost/ capacity= 443,386,000 €/ (20 year x 739,130 ton) = 27.70 €/ton

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Scenario 2b -Anaerobic digestion

Amount of incoming wet waste to microwave pretreatment unit = 31 kg/ca. year (STAN

Scenario-2b)



Design Capacity: 0.085x 365 x 4,050,028=125,652 ton/year

Initial capital investment = 20,000,000 € (Tsilemou K., et.al., 2006)



Operational cost: 30 €/ton (Tsilemou K., et.al., 2006)


Total operating cost: 3,769,600 €/ year x 20 year= 75,391,200 €/year

Total cost: 20,000,000 +24,000,000 + 75,391,200 =119,391,200 €/ 20 year

Total cost/ capacity= 119,391,200 €/ (20 year x 125,652 ton)= 47.50 €/ton

Revenue from sales of energy: 15 € /ton

Anaerobic digestion capacity: 125,652 ton/year

Moisture content: 60%

The amount of dry solid: 125,652 x 0.40 = 50,260 ton/year

The amount of volatile solid: 35,183 ton/year

Volatile solid reduction: 60% Thus,

The amount of destroyed volatile solid production: 21,110 ton /year

Methane yield (m3/kg): 0.36

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Methane yield (m3): 21,110 ton/year x0.36 m3/kg x 103kg/ton= 7,599,600 m3CH4/year

One cubic metre of CH4 has a heating value of around 22,400 kilojoules/m3.

7,599,600 m3CH4/year x 22,400 kilojoules/m3= 1.70231 x 1011 kilojoules

1.70231 x 1011 kilojoules = 47,286,400 kwh

47,286,400 kwh x 4 cent= 1,891,456 €/year

1,891,456 €/year / 125,652 ton/year = 15 €

Net cost for anaerobic digestion process = 47.5-15 = 32.5 €/ton

Scenario 2b -Composting

Design capacity of composting plant

Amount of incoming wet waste to composting plant from anaerobic dig. plant=198 kg/ca. year

(STAN Scenario-2b)

198 kg/ca. year=0. 54 kg/ ca.day.


Design Capacity: 0.54x 365 x 4,050,028 = 798,260 ton/ year

Initial capital investment (€)=Y= 4000 x W0.7 =4000 x (798,260)0.7 =54,145,335€


Depreciation cost: 64,974,400 €/20 years




Total cost: 54,145,335 + 64,974,400 + 319,304,000 = 438,423,735 €/ 20 year

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Total cost/ capacity= 438,423,735 €/(20 year x 798,260 ton) = 27.46 €/ton

Scenario 2b –Microwave pretreatment

Microwave Features

Frequency: 2450 Hz

Power: 750 W( adjustable)

Batch operation

Amount of incoming wet waste to microwave pretreatment = 204 kg/ca. year (STAN

Scenario-2b)



Design capacity: 0.5589 x 365 x 4,050,028 = 826,200 ton / year

Initial capital investment (€)=Y= 600.000 €


Depreciation cost: 720.000€/ 20 years

Total operating cost: 500.000 €/ year x 20 year=10,000,000 €/year

Total cost: 600,000 + 720,000 + 10,000,000 = 11,320,000 €/ 20 year

Total cost/ capacity= 11,320,000 €/ 826,200 ton/year =13,70 ton

Cost of Harmandali Landfill Site

Amount of incoming mixed waste to lanfill site

1.28 kg/ca. year (STAN Status quo)

Total amount of MSW=32,000,000 ton

Initial capital investment (€)=1,600,000 €

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Total operating cost: 6 €/ ton x 32,000,000 ton = 192,000,000 €/ 20 year

Total cost: 1,600,000 €+ 1,920,000 €+192,000,000 €=195,520,000

Total cost/ capacity= 195,520,000 €/ 32,000,000 =6,11 €/ton

Total cost / capita.year=195,520,000 / 4,050,028 x 20 = 2.4 €/ton.ca

Table 10. Estimated total costs

Scenarios Composting (€/ton)

Anaerobic Digestion

(€/ton)

Microwave Pretreatment

(€/ton)

Revenue from sales energy

(€/ton)

Total cost (€/ton)

Status Quo (Landfill)

6.11

Scenario1 (Composting)

27.40 27.40

Scenario2a (compost+anaerobic digestion)

27.70 46.57 10.00 64.27

Scenario2b (microwave+compost+anaerobic digestion)

27.46 47.50 13.70 15.00 103.66

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Evaluations

Table11. Summary of outputs of Status Quo and Scenarios

CO2+H20

kg/ca.a

Biogas

CO2+CH4

kg/ca.a

CO2-eq

kg/ca.a

CH4-eq

kg/ca.a

Compost

kg/ca.a

Compost

Residues

kg/ca.a

Status Quo 70

Scenario1 151 23 65 28

Scenario2a 140.48 20.40 30 44.12 19

Scenario2b 150 5.20 25.50 48 20

All scenarios were analysed in terms of their impacts on costs and goal-oriented parameters.

The ratio of organic waste is circa 46% of total MSW. If the organic wastes are sent to landfill

site after treatment, landfill volume will decrease 40%, greenhouse gas emissions CO2-eq.

will be reduced within the ratio of 30%, also. Disposal ratio of organic wastes will reduce

approximately within the ratio of 95%. Thus, direct impact on environment and indirect effect

of human health of landfill sites will potentially decrease. The cost of landfill site will be

decreased within the ratio of 40%. When wastes are collected separately, recyclables and

compost product can be reused (Table 11-12 and Figure 27).

Table 12. Comparison of status quo and scenarios MSWM in Izmir

Status Quo Scenario1 Scenario2a Scenario2b

Greenhouse gas emissions (CO2-equivalent) 35 25 10 5

Material recycling rate(compost) n.d. n.d.+21 n.d.+21 n.d.+24 Disposal rate 100 9 9 10

Reduction of Landfill volume required for organic wastes 0 40 42 42

Cost / Capacity-year (€) 6.11 27.4 64.27 103.66

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Figure 27.Changes of goal oriented parameters for different scenarios of IMSWM in Izmir

Units: Greenhouse gas emissions (CO2- equivalent), kg CO2/ ca. year

Material recycling rate ; recyled material per total input, in tons

Landfill rate; recyled material per total input, in tons

Reduction of landfill volume required for organic wastes, in tons.

35

0

100

0 6,11

25 14

6

40 27,4

10 9 4

42

64,27

5 10 4

42

103,66

0

20

40

60

80

100

120

Greenhouse gasemissions (CO2-

equivalent)

Material recycling rate Disposal rate Reduction of Landfillvolume required for

organic wastes

Cost / Capacity(Euro)

IZMIR Status Quo Scenario1 Scenario2a Scenario2b

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7 Conclusions

The aim of MSW management is protect human health and the environment, and to conserve

resources. The most cost-effective method is the first scenario to reach the objectives of solid

waste management. Because, according to foundings, municipality has been gathering 13.83

€/ca.year for whole solid waste management. Izmir municipilaty needs 27.4 €/ca.year to fulfill

Scenario1. Thus, municipilaty should spend 21.4 €/ca.year more. This cost is also not

included collection and transport expenses. It is recommended that Izmir municipilaty must

determine and organize its economic capacity for waste management system to reach waste

management goals.

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8 References

Adani, F., Scatigna, L., Genevini,P., 2000. Biostabilization of mechanically separated

municipal solid waste fraction. Waste Management Res. 15, 471-477.

Agamuthu, P., Hansen J. A., 2007. Universities in capacity building in sustainable

development: focus on solid waste management and technology. Waste Management Res.

25, 241-246.

Ahn, H.K., Richard, T.L., Choi, H.L., Mass and thermal balance during composting of poultry

manure- Wood shavings mixture at different aeration rates. Process Biochemestry 42, 215-

223.

Andersan, J.K., Boldrin, A., Christensen, T.H., Scheutz, C., 2011. Mass balances and life

cycle inventory of home composting of organic waste. Waste management 28, 1010-1020.

Angelidaki, I., Batstone, D.J., 2011. Solid Waste Technology & Management. Volume 2.

Blackwell Publishing Ltd.

Baccini, P., Brunner, P.H., 2012. Metabolism of the Anthroposphere.The MIT Press.

Banks, C.J., Chesshire, M., Heaven, S., Arnold, R., 2010. Anaerobic digestion of source-

segregated domestic food waste: Performance assessment by mass and energy balance.

Bioresource Technology 102, 612-620.

Baptista, M., Antunes, F., Goncalves, M.S., Morvan, B., Silveira, A., 2010. Waste

Management 30, 1908-1921.

Berkun, M., Aras, E., Nemlioglu, S., 2005. Disposal of solid waste in Istanbul and along the

Black Sea coast of Turkey. Waste Management 25, 847-855.

Boldrin, A., Christensen, T.H., 2011. Solid Waste Technology & Management. Volume 2.


Bouallagui, H., Cheikh, R.B., Marouani, L., Hamdi, M., 2003. Mesophilic biogas production

from fruit and vegetable waste in tubular digester. Bioresour. Technol. 86, 85–89.

Brunner, P.H., Rechberger, H., 2004. Material Flow Analysis. CRC Press LLC.

TU Vienna 80

Brunner, P.H., Fellner, J., (2007). Setting priorities for waste management strategies in

developing countries, Waste Management & Research 25, 234-240.

Brunner, P.H., Beckmann, M., Born, M., Merillot, J.-M., Vehlow, J., 2013. Research needs for

waste management. Institute of Water Quality, Resources and Waste, Vienna University of

Technology.

Chaturvedi, B., 2010. Solid Waste Management in the World`s Cities: Water and Sanitation in

the World´s Cities. United Nations Human Settlements Programme (UN-HABITAT)2010.

Christensen, T.H., 2011. Solid Waste Technology & Management. Volume 1-2. Blackwell

Publishing Ltd.

Datta, A.K., Anantheswaran, 2001. Handbook of microwave technology for food

applications. Marcel Dekker, Inc.

Diaz, L.F., Bertoldi, M., 2007. Compost Science and Technology. Elsevier Science.

De Baere, L., Vandevivere, P., Verstraete, W., 2004. Anaerobic Digestion of Solid Waste.

De Baere, L., Mattheeuws, B., 2010. Anaerobic Digestion of MSW in Europe. BioCycle

February 2010, 24.

Fruteau de Laclos, H., Desbois, S. and Saint-Joly, C. (1997) Anaerobic digestion of municipal

solid organic waste : Valorga full-scale plant in Tilburg, The Netherlands. In Proc. 8th Int.

Conf. on Anaerobic Dig., held in Sendai, May 25-29, 1997, vol. 2, pp. 232-238, Int. Assoc.

Wat. Qual.

Getahun, T., Nigusie, A., Entele, T., Gerven, T.V., Van der Bruggen, B., 2012. Effect of

turning frequencies on composting biodegradable municipal solid waste quality. Resources,

Conservation and Recycling 65, 79-84.

Golueke, C.G., & McGauhey, P.H. (1953).Reclamation of municipal refuse by composting.

Sanitary Engineering Research Laboratory, University of California, Berkeley, USA,

Technical Bulletin No. 9.

Hui, Y., Li´ao, W., Fenwei, S., Gang, H., 2006. Urban solid waste management in Chongqing:

Challenges and opportunities. Waste management 26, 1052-1062.

TU Vienna 81

Insam, H.,Bertoldi. M., 2007. Compost Science and Technology. Elsevier Science

Jackowiak, D., Frigon, J.C., Ribeiro, T., Pauss, A., Guiot S., 2010. Enhancing solubilisation

and methane production kinetic of switchgrass by microwave pretreatment. Bioresource

Technology, 102, 3535-3540.

Kalamdhad, A.J., Kazmi A.A., 2009. Effects of turning frequency on compost stability and

some chemical characteristics. Chemosphere 74, 1327-1334.

Kanat, G., 2010. Municipal solid waste management in Istanbul. Waste Management 30,

1737-1745.

Khalid, A., Arshad, M., Anjum, M., Mahmood, T., Dawson, L., 2011. The anaerobic digestion

of solid organic waste. Waste Management. 31, 1737-1744.

Krogmann, U., Körner, I., Diaz, L.F., 2011. Solid Waste Technology & Management. Volume

2. Blackwell Publishing Ltd.

Liu, T. and Ghosh, S. (1997) Phase separation during anaerobic fermentation of solid

substrates in an innovative plug-flow reactor. In Proc. 8th Int. Conf. on Anaerobic Dig., held

in Sendai, May 25-29, 1997, vol. 2, pp. 17-24, Int. Assoc. Wat. Qual. Lossin, R.D. (1970).

Compost studies.Compost Sci., 11, 16.

Marin, J., Kennedy, K.J., Eskicioglu, C., 2010. Effect of microwave irradiation on anaerobic

degradability of model kitchen waste. Waste Management 30, 1772-1779.

Maso, M.A., Blasi, A.B., 2008. Evaluation of composting as a strategy for managing organic

wastes from a municipal market in Nicaragua. Bioresource Technology 99, 5120-5124.

Mason, I.G., 2006. Mathematical modelling of the composting process: a review. Waste

management 26, 3-21.

Mason, I.G:, 2008a. An evaluation of substrate degradation patterns in the composting

process. Part 1: profiles at constant temperature. Waste management 28, 1751-1765.

TU Vienna 82

Melikoglu, M., 2013. Vision 2023: Assessing the feasibility of electricity and biogas production

from municipal solid waste in Turkey. Renewable and Sustainable Energy Reviews 19, 52-

63.

Nas, S.S., Bayram, A., 2007. Municipal solid waste characteristics and management in

Gumushane. Waste Management 25, 2435-2442.

Niese, G. (1963).Experiments to determine the degree of decomposition of refuse compost

by 1st self-heating capability. Giessen, Germany, International Bulletin 17.

Obrist, W. (1965).Enzymatic activity and degradation of matter in refuse, digestion:

suggested new method for microbiological determination of the degree of

digestion.International Research Group on Refuse Disposal, Bulletin 24

Official Gazette. Law for metropolitan municipalities. Law no: 5216. Accepted on 10.07.2004,

Ankara, Turkey.

Oleszkiewicz, J.A. and Poggi-Varaldo (1997). High-solids anaerobic digestion of mixed

municipal and industrial wastes. J. Environ. Eng. 123: 1087-1092.

Palmisano, A.C., Barlaz, M.A., 1996. Microbiology of Solid Waste, CRC Press.

Palmowski, L. and Müller, J. (1999) Influence of the size reduction of organic waste on their

anaerobic digestion. In II Int. Symp. Anaerobic Dig. Solid Waste, held in Barcelona, June 15-

17, 1999 (eds. J. Mata-Alvarez, A. Tilche and F. Cecchi), vol. 1, pp. 137-144.

Pesta. G., 2007. Utilization of By- Products and Treatment of Waste in The Food Industry.

pg. 53-71.

Pognani, M., Barrena, R., Font, X., Sanchez A., 2012. A complete mass balance of a

complex combined anaerobic/ aerobic municipal source-separeted waste treatment plant.

Waste Management, 2012, 799-805.

Rolle, G., & Orsanic, E. (1964).A new method of determining decomposable and resistant

organic matter in refuse and refuse compost. International Research Group on Refuse

Disposal, Bulletin 21.

TU Vienna 83

Schievano, A., D´Imporzano, Salati, S., Adani, F., 2011. On-field study of anaerobic digestion

full- scale plants (Part I): An on-field methodology to determine mass, carbon and nutrients

balance. Bioresource Technology 102, 7737-7744.

Schubert, H., Regier, M., 2005. The microwave processing of foods. Woodhead

Publishing Limited and CRC Press LLC.

Schulze, K.F. (1960). Rate of oxygen consumption and respiratory quotients during the

aerobic composting of synthetic garbage.Compost Sci., 1, 36

Stegmann, R., 2005. Mechanical Biological Pretreatment of Municipal Solid Waste.

Proceedings Sardinia 2005, Tenth International Waste Management and Landfill Symposium

S. Margherita di Pula, Cagliari, Italy, 3-7 October 2005.

Stentiford, E., Bertoldi, M., 2011. Solid Waste Technology & Management. Volume 2.


Tinmaz, E., Demir, I., 2005.Research on solid waste management system: To improve

existing situation in Corlu Town of Turkey, Waste Management 26, 307-314.

Tsilemou K., Panagiotakopoulos, K., 2006. Approximate cost functions for solid waste

treatment facilities, Waste management 24, 310-322.

Turan, N.G., Çoruh, S., Akdemir, A., Ergun, O.N., 2009. Municipal solid waste management

strategies in Turkey. Waste Management 29, 465-469.

McDougall, F., White, P., Franke, M., and Hindle, P., 2001. Integrated Solid Waste

Management: a Life Cycle Inventory. Published by Blackwell Science, Oxford, UK

Vandevivere, P., De Baere, L., Verstraete, W., 2010. Types of anaerobic digesters for solid

wastes.

Vazquez, M., C., Bagley, D.M., 2002. Evaluation of the performance of different anaerobic

digestion technologies for solid waste treatment. Depertment of Civil Engineering, University

of Toronto.

TU Vienna 84

Walker, L.R., Cord-Ruwisch, R., Sciberras, S., 2011. Performance of a commercial – scale

dicom demonstration facility treating mixed municipal solid waste. Proceedings of the

International Conference on Solid Waste 2011, Hong Kong SAR, P.R. China, 2-6 May 2011.

Tsilemou, K., Panagiootakopoulos, D., 2006. Approximate cost functions for solid waste

treatment facilities. Waste Management Res. 24, 310-322.

Turkstat ,2010, 2013. Turkish Statistical Institute.

Williams, P. T., 2005. Waste Treatment and Disposal. John Wiley & Sons.

Worrell, W. A., Vesilind, P.A., 2012. Solid Waste Engineering, Cengage Learning.

Zhang, H., Matsuto, T., 2010. Mass and element balance in food waste composting facilities.

Waste management 30, 1477-1485.

Zhang, H., Matsuto, T., 2010, Comparison of mass balance, energy consumption and cost of

composting facilities for different types of organic waste. Waste Management 31, 416-422.

Zucconi, F., Pera, A., Forte, M., & de Bertoldi, M. (1981a). Evaluating toxicity of immature

compost.Biocycle, 22(2), 54–57.

Zucconi, F., Forte, M., Monaco, A., & de Bertoldi, M. (1981b). Biological evaluation of

compost maturity.Biocycle, 22(4), 27–29.

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